Corporate Investments and Funds Held For Clients (Narrative) (Details) - USD ($)	9 Months Ended		12 Months Ended
	Mar. 31, 2020		Jun. 30, 2019
Debt Securities, Available-for-sale [Line Items]
Earliest Corporate bond debt maturity date	April 2020
Latest corporate debt maturity date	March 2030
Fair market value	$ 24,023,600,000	[1]	$ 24,859,100,000	[2]
Earliest U.S. treasury maturity date	April 2020
Latest U.S treasury maturity date	December 2029
Client fund obligation repayment period	1 year
Client funds obligations	$ 30,359,000,000.0		29,144,500,000
Client funds held in grantor trust	$ 27,689,800,000		$ 26,648,000,000.0
Client funds investments with original maturities	ninety days or less
Percentage of the available-for-sale securities were rated AAA Or AA	77.00%
Fair Value, Inputs, Level 1 [Member]
Debt Securities, Available-for-sale [Line Items]
Fair market value	$ 0
Fair Value, Inputs, Level 3 [Member]
Debt Securities, Available-for-sale [Line Items]
Fair market value	0
Federal Home Loan Banks
Debt Securities, Available-for-sale [Line Items]
Fair market value	648,500,000
Federal Farm Credit Banks
Debt Securities, Available-for-sale [Line Items]
Fair market value	698,400,000
U.S. government agency securities
Debt Securities, Available-for-sale [Line Items]
Fair market value	91,700,000
Fixed Rate Credit Card
Debt Securities, Available-for-sale [Line Items]
Fair market value	1,483,600,000
Asset-Backed Auto Loan Receivables
Debt Securities, Available-for-sale [Line Items]
Fair market value	2,045,200,000
Asset-Backed Equipment Lease Receivable
Debt Securities, Available-for-sale [Line Items]
Fair market value	391,500,000
Rate Reduction
Debt Securities, Available-for-sale [Line Items]
Fair market value	121,000,000.0
Supranational Bonds
Debt Securities, Available-for-sale [Line Items]
Fair market value	190,200,000
Commercial Mortgage Backed Securities
Debt Securities, Available-for-sale [Line Items]
Fair market value	$ 859,000,000.0

[1] Included within available-for-sale securities are corporate investments with fair values of $3.2 million and funds held for clients with fair values of $24,020.4 million. All available-for-sale securities were included in Level 2 of the fair value hierarchy.

[2] Included within available-for-sale securities are corporate investments with fair values of $271.9 million and funds held for clients with fair values of $24,587.2 million. All available-for-sale securities were included in Level 2 of the fair value hierarchy.